Eos is a source for news and perspectives about Earth and space science and run by AGU (American Geophysical Union). Eos Editors’ Highlights are part of a collection of some of the most interesting and impactful research published in AGU journals. Recently, our JGR-Earth Surface paper “Denudation rate changes along a fast‐eroding mountainous river with slate headwaters in Taiwan from 10Be (meteoric)/9Be ratios” was selected for Editors’ Highlights. This study was conducted via collaboration between Tongji University and Prof. Friedhelm von Blanckenburg and Dr. Hella Wittmann at German Research Centre for Geosciences (GFZ).

The novel 10Be (meteoric)/9Be system, where 10Be is delivered by precipitation and stable 9Be is released by weathering, provides denudation rates over weathering-erosion timescales. The new tool is applicable to quartz-poor lithologies, e.g. mafic rock and claystone, which are not readily accessible by the commonly used in situ-produced 10Be in quartz. We provide a first application of this proxy to a tectonically-active mountainous river, the Zhuoshui River in Taiwan. Taiwan Rivers supply a disproportionately high suspended and dissolved flux to the oceans and are often underlain by fine-grained shale/slate. 10Be (meteoric)/9Be-derived denudation rates (Dmet) from the Zhuoshui Catchment are highest in the slate-dominated headwaters (4-8 mm/yr), and much lower (1-2 mm/yr) along the mid-lower reaches with mixed lithologies. At the basin-wide scale, we find a poor correlation between Dmet and basin-averaged channel steepness despite a small climatic gradient. Because large lithological heterogeneities exist in this basin, we invoke a lithological effect to explain this poor correlation. Relying on a revised stream power incision model that incorporates rock erodibility, the resulting lithology- and runoff- adjusted ksn (kLrsn) can be reconciled with denudation rates with the highest erodibility predicted to prevail in the Miocene slate of low metamorphic grade and high fracture density. This model suggests that the lithological heterogeneity can alter the coupling between surface denudation and channel morphology. On a broader perspective, the successful application of the 10Be (meteoric)/9Be proxy shows its applicability as a tracer for erosion and sediment transport processes in fast-eroding mountain belts underlain by slate lithologies.

JGR-ES editor Mikael Attal wrote in “Editors’ Highlight”: “…This study bridges a significant gap: it demonstrates that meteoric 10Be can be used to quantify erosion rates in catchments with a range of lithologies exposed. It proposes a new framework to quantify differences in rock resistance to erosion and demonstrate their impact on landscape steepness, with implications for retrieving erosional signals from topographic data.”

Cite: Deng, K., Yang, S., von Blanckenburg, F., & Wittmann, H. [2020]. Denudation rate changes along a fast‐eroding mountainous river with slate headwaters in Taiwan from 10Be (meteoric)/9Be ratios. Journal of Geophysical Research: Earth Surface, 125, e2019JF005251.

Eos Editors’ Highlight:https://eos.org/editor-highlights/meteoric-10be-reveals-lithological-control-on-erosion-rates

Full article:https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019JF005251